Portfolio Experiment: Equal Weight vs Market Cap S&P 500 ETFs

By Chanuka Geekiyanage Oct 20, 2026

Choosing between an equal weight and a market cap S&P 500 ETF decides how much of your money rides on a handful of mega-cap stocks. The Vanguard S&P 500 ETF (VOO) and the Invesco S&P 500 Equal Weight ETF (RSP) hold the same 500 companies, yet RSP has trailed badly over the past decade while leading for stretches of 2026. This article compares cost, concentration, returns, taxes, and risk so you can decide which fund fits your portfolio, or whether a split makes more sense.

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Same 500 Stocks, Two Different Bets

VOO weights each company by market value, so bigger companies get bigger positions. RSP gives each stock roughly 0.2% and resets to that level every quarter.

The gap in what you own is large. Apple, with a market cap of roughly $4 trillion, has the same weight as Best Buy, with a market cap of about $13 billion, at approximately 0.18% each inside an equal weight fund.

Fund	Weighting	Expense Ratio	Top-10 Exposure	Best For
RSP	Equal, rebalanced quarterly	0.20%	About 3%	Satellite holding, tax-deferred accounts
VOO	Market cap	0.03%	About 37% to 40% (index level)	Core holding, taxable accounts
IVV	Market cap	Similar to VOO	About 37% to 40% (index level)	Same role as VOO
SPY	Market cap	About 0.09%	About 37% to 40% (index level)	Active traders, options users

Top-10 figures come from Invesco’s 37% estimate and etf.com’s roughly 39%, and ChartRow shows RSP’s top ten at 3.2% as of April 2026. Fees are as reported in the sources listed under References.

Why Concentration Drives the Debate

The case for equal weight is a case against concentration. The 10 largest companies in the S&P 500 now account for 37% of the index, up from less than 20% in 2014. If you want to understand what that means for your downside, our breakdown of AI stock concentration and S&P 500 risk covers it in detail.

Valuation is the second difference. As of 31 August 2026, the S&P 500 had a P/E of 26.3, a 29% premium to the equal weight index. Cheaper does not mean better, but it does explain why RSP behaves like a value-tilted fund.

Equal weight is also not a pure diversification win. You trade top-heavy exposure for a tilt toward smaller, more cyclical companies that react more to credit conditions and economic slowdowns.

What the Returns Show

The long-run record favors market cap weighting in the last decade, and the recent record is mixed. Over ten years, RSP returned 206.76% versus 314.79% for VOO, and over five years 53.18% versus 86%.

Year	RSP	VOO	Gap (RSP minus VOO)
2022	-11.62%	-18.17%	+6.55 points
2023	13.70%	26.32%	-12.62 points
2024	12.79%	24.98%	-12.19 points
2025	11.21%	17.82%	-6.61 points

Yearly figures are from PortfoliosLab. Compounding them, my calculation gives RSP about +26% and VOO about +52% across 2022 to 2025.

Here is the simple experiment. Put $10,000 in each fund ten years ago and, using the ten-year figures above, RSP grows to roughly $30,700 and VOO to roughly $41,500. That is a gap of about $10,800, and the 0.17% fee difference explains only a small piece of it.

2026 complicates the story. Mid-year, RSP was returning about 13.0% year to date versus roughly 10.2% for VOO. By late September, a ShareTrader comparison showed RSP up 10.21% year to date against 13.35% for VOO, with RSP down 4.81% over the month to September 25. Treat these as snapshots and verify with your broker, because the lead changed hands within a few months.

The longer history is closer than the last decade suggests. Since 2003, the equal weight index outperformed the cap-weighted index by 0.98% annualized, per Invesco, which sells the equal weight fund. Independent research is less generous: the equal weight index beat its parent in only 10 of 20 years, and the cap-weighted index had the higher Sharpe ratio. The Sharpe ratio measures return per unit of risk.

The Hidden Costs of Equal Weight

The fee gap is the obvious cost. On $10,000, RSP’s 0.20% versus VOO’s 0.03% is about $17 a year.

The less obvious costs matter more:

Rebalancing drag: RSP sells winners and buys laggards every quarter. That works when leaders fade and hurts when they keep running.
Turnover: One data aggregator reports 27% turnover for RSP as of April 2026, against typically under 5% for VOO. More trading means more cost inside the fund.
Tax friction: Invesco says RSP has not paid a capital gains distribution since its 2003 inception, based on data as of September 2023. Check the latest distribution history before holding it in a taxable account.
Sector tilt: Technology is about 14% of RSP versus roughly 33% of VOO, so you take on more industrials, financials, and utilities exposure.

RSP, VOO, and SPY Compared

RSP is the equal weight pick. Its strengths are low single-stock concentration and a higher dividend yield, around 1.5% versus about 1.1% for VOO. Its weaknesses are the fee, the turnover, and a long stretch of lagging when mega caps lead.

VOO and IVV are the market cap core. Both offer identical S&P 500 exposure at 0.03%. You accept top-heavy exposure, and if AI spending disappoints, you feel it most here.

SPY matters for trading, not holding. Its roughly 0.09% fee is about three times VOO’s, and its main advantage is liquidity and options depth. For a buy-and-hold investor there is little reason to pay more.

If you want a third route, other funds exist. Goldman Sachs Equal Weight U.S. Large Cap Equity ETF (GSEW) and iShares MSCI USA Equal Weighted ETF (EUSA) are alternatives, and the Tema S&P 500 Historical Weight ETF (DSPY) uses historical averages to set position sizes. Compare their fees and trading volume before treating them as RSP substitutes.

Which One Fits Your Situation

Before you decide, check these items for any fund you plan to hold:

Top-10 weight and sector weights today, not last year
Expense ratio and the dollar cost on your balance
Capital gains distribution history, if the account is taxable
Bid-ask spread and daily volume
How much of your wealth is already in tech through your job or stock options

If you are still choosing between funds and picking stocks yourself, read our guide on ETFs versus individual stocks first.

User Type	Recommended Option	Reason
Beginner, one fund only	VOO or IVV	Lowest cost, simplest, no timing decision
Worried about AI concentration	70% VOO, 30% RSP	Cuts mega-cap weight without a full switch
IRA or 401(k) investor	RSP sleeve is reasonable	Tax friction from turnover is not a concern
Taxable account, cost sensitive	VOO or IVV	Lower fees and lower turnover
Active trader	SPY	Liquidity and options market
Already heavy in tech stocks	Add RSP	Reduces overlap with your existing holdings

Common Mistakes

Switching after one good year. RSP’s strong stretch in early 2026 was followed by a sharp reversal within months. One year tells you very little.
Assuming equal weight means safer. It lowers single-stock risk but raises small and mid-cap exposure, and it still falls in a bear market.
Holding both and calling it diversification. Both funds own the same 500 stocks, so you are changing weights, not holdings.
Ignoring account type. Turnover matters more in a taxable account than in an IRA.
Comparing price returns to total returns. RSP pays a higher yield, so use total return when you compare.

How to Run Your Own Version

A fair test is a core and satellite split. Hold VOO or IVV as the core and put 20% to 40% in RSP, then rebalance once a year.

Judge the result after at least five years, not 12 months. Track after-tax return, not just headline return, and write down in advance what outcome would make you change the split.

My Take

For most investors, VOO or IVV should be the core holding. The fee is tiny, the track record is strong, and you avoid betting on a rotation that may not arrive.

RSP earns a place as a satellite, not a replacement, if you hold a large amount of tech through other accounts or fear an AI spending pullback. I would hold it in an IRA or 401(k) first, and I would skip it as a sole fund because a decade of lagging is not a small risk.

Before buying RSP, I would check the current top-10 weight of the S&P 500, the fund’s distribution history, and the spread at the time I trade. If you want small and mid-cap exposure on purpose, a dedicated mid-cap fund may be a cleaner choice than relying on equal weight to deliver it.

Conclusion

Market cap weighting has been the better performer over the past five and ten years, and it costs less. Equal weight has a real case when concentration is high and leadership broadens, but it comes with a higher fee, more turnover, and a tilt toward smaller, more cyclical companies.

The practical step is simple. Keep a low-cost market cap fund as your core, decide whether a 20% to 40% equal weight sleeve fits your risk and account type, and review the split yearly instead of reacting to short-term swings.

FAQs

1. Is RSP better than VOO right now?

It depends on the window you measure. RSP led for much of the first half of 2026, but a September 25, 2026 comparison showed VOO ahead year to date at 13.35% versus 10.21%.

2. Does equal weight actually reduce risk?

It reduces single-stock concentration, since the top 10 holdings are about 3% of RSP versus roughly 37% of the S&P 500. It does not reduce overall market risk, and it adds a tilt toward smaller, more cyclical companies.

3. Is the 0.17% fee gap worth paying?

On $10,000 the gap between RSP’s 0.20% and VOO’s 0.03% is about $17 a year, which is small next to the return gap in either direction. It is worth paying only if you want the equal weight exposure itself, not because you expect it to win.

4. Should I hold RSP in a taxable account?

Invesco reported no capital gains distribution since 2003 as of September 2023, but RSP’s turnover is higher than VOO’s. Check the recent distribution history, or place it in an IRA or 401(k) when you can.

5. Can I own both RSP and VOO?

Yes, and a core and satellite split is the simplest way to test equal weight without betting everything on it. You still own the same 500 stocks, so the split changes your weights, not your holdings.

References

Invesco, S&P 500 Equal Weight ETF (RSP) fund page: https://invesco.com/us/en/etf/sp-500-equal-weight-rsp.html

ETF.com, As Mega Caps Stall, Equal Weight Makes a Comeback: https://www.etf.com/sections/features/mega-caps-stall-equal-weight-makes-comeback

PortfoliosLab, RSP vs VOO comparison: https://portfolioslab.com/tools/stock-comparison/RSP/VOO

ShareTrader, RSP vs VOO comparison: https://sharetrader.com.au/etf-us/rsp/compare/etf-us/voo

ChartRow, S&P 500 Equal Weight concentration: https://chartrow.com/sp500-equal-weight/concentration

KoalaGains, RSP fund data: https://koalagains.com/etfs/NYSEARCA/RSP

Piranha Profits, SPY/VOO vs RSP: https://www.piranhaprofits.com/blog/rsp-vs-spy-voo

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About the Author: Chanuka Geekiyanage

Chanuka is a content writer, editor and contributor at Panaprium, specializing in long-form editorial articles. He conducts in-depth research and produces well-structured, carefully edited content with a strong focus on clarity, SEO best practices, and consistent formatting. His work spans lifestyle, fashion, wellness, and technical topics, and all articles are reviewed and refined to meet Panaprium’s editorial standards.

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